14. Adrenergic receptors (adrenoceptors) - DOPAMIN Flashcards by Aurora H

Characteristics of adrenoceptors: α1 receptor
-> What is the main effect?

Constriction/Contraction

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Characteristics of adrenoceptors: α1 receptor
-> Main effect: Constriction/Contraction

Blood vessels, bronchi, uterus, sphincters (GI, bladder),
iris (radial muscle)→midriasis
Liver hepatocytes: glycogenolysis

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Examples of clinical use of adrenoceptors: α1 receptor

agonist:
hypotension
nasal congestion
used as a vasoconstrictor in local anesthetics to decrease their absorption

antagonist: hypertension; benign prostatic hypertrophy

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Characteristics of adrenoceptors: α2 receptor
-> Main effects

presynaptic: feedback: inhibits NE release inhibits sympathetic (adrenergic) outflow

postsynaptic: vasoconstriction
pancreatic beta cells: decrease insulin secretion platelets: aggregation

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Characteristics of adrenoceptors: α2 receptor
-> Example of clinical use (agonist)

hypertension treatment
(opiate) withdrawal treatment
vasomotor instability (‘hot flushes’)

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Characteristics of adrenoceptors: α2 receptor
-> Example of clinical use (antagonist)

(not used clinically claimed to be aphrodisiac)

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Glucose regulation of insulin secretion by ___- (which type of cells)

Pancreatic beta cell

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Glucose regulation of insulin secretion by pancreatic beta cells

1/ Glucose transporter GLUT2
2/ ATP-gated K+ channel
3/ Voltage-gated Ca2+ channel

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Where are Incretins (Glucagon-like peptide 1 [GLP-1]) released?

They are released from neuroendocrine cells of the gastrointestinal tract

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Incretins (Glucagon-like peptide 1 [GLP-1])
are released from neuroendocrine cells of the gastrointestinal tract following food ingestion and amplify ___ and ___

glucose-stimulated insulin secretion and suppress glucagon secretion.

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What are GLP-1 agonists?

pharmacologic agents that prolong the activity of endogenous GLP-1 enhance insulin secretion.

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What does this slide indicate?

Structure of the β-adrenergic receptor in the active states and its associated trimeric G protein

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What does this slide indicate?

Structure of the β-adrenergic receptor in the active states and its associated trimeric G protein

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Characteristics of adrenoceptors: β1 receptor
-> What are the main effects of adrenoceptors: β1 receptor?

increase heart rate, force of contraction renin release
lipolysis

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Characteristics of adrenoceptors: β1 receptor
-> What are the examples of clinical use (agonist)?

severe cardiac failure

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Characteristics of adrenoceptors: β1 receptor
-> What are the examples of clinical use (antagonist)?

antagonist (beta blockers):
prevent heart ischemia

hypertension social fobia

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Characteristics of adrenoceptors: β1 receptor
-> Identify 1

ACE inhibitors

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Characteristics of adrenoceptors: β1 receptor
-> What can inhibit AT1 receptors?

Angiotensin II
AT1 subtype receptor antagonists

Characteristics of adrenoceptors: β2 receptor
-> What is the main effect?

Main effect: dilate/relax

blood vessels, bronchi, uterus, GI, sphincter (bladder), ciliary muscle→miosis

Liver, muscle: glycogenolysis

Mast cells: inhibition of histamine release

Characteristics of adrenoceptors: β2 receptor
-> What is an example of clinical use - agonist?

bronchodilators (asthma)
(also inhibit mediator release from mast cells)

Characteristics of adrenoceptors: β2 receptor
-> Identify

cAMP-dependent protein kinase

Characteristics of adrenoceptors: β2 receptor
-> What is happening at 1 & 2?

1/ Myosin light chain kinase is active
2/ Myosin light chain is phosphorylated

Characteristics of adrenoceptors: β2 receptor
-> What is happening here?

reduced sensitivity of MLCK to the Ca2+ -calmodulin complex

Characteristics of adrenoceptors: β2 receptor
-> What will happen at 1 & 2?

1/ contraction
2/ smooth muscle relaxation

Characteristics of adrenoceptors: β3 receptor -> What is the main effect?

relax bladder lipolysis thermogenesis

Examples of clinical use of adrenoceptors: β3 receptor

agonist: overactive bladder

Identify

Characteristics of VMAT 2 - vesicular monoamine transporter 2?

Broad substrate-specificity to biogenic amines (tryptamine, tyramine, amphetamine – compete with endogenous catecholamine)

Identify 1 & 2

1/ Dihydroxyphenylacetic acid (DOPAC) 2/ Homovanilic acid (HVA)

List Dopaminergic receptors types

Dopaminergic receptors -> The role of D1 type

Dopaminergic receptors -> The role of D2 type

Examples of endogenous Neurotoxins

metabolites of catabolism: DOPAL

Exogenous neurotoxins -> The mechanism of MPTP (1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine)

Taken up by dopaminergic nerve terminals – metabolized by MAO-B -> 1-methyl-4-phenyl-pyridinium (MPP+) - active toxic metabolite – complex I inhibitor

Exogenous neurotoxins -> Where do MPTP present?

In the i.v. narcotic drug heroin as a contaminant

The role of Cycad tree

tropical seed contains ß-methyl-amino- L-alanin (BMAA) produced by cyanobacteria found in the roots of cycads

does Dopamine cross the blood-brain barrier?

Dopamine does not cross the blood-brain barrier (BBB)